First use of the maleamate(−1) ligand in coordination chemistry: Dinuclear copper(II) complexes with N-donors and their interesting ‘organic’ chemistry

Abstract

A systematic investigation of the reactions of 3d-metal ions with the maleamate(−1) ligand (HL −) in the presence of mono- , bi- or tridentate chelating N-donors has been initiated and the first results are described. Reaction schemes involving Cu(ClO 4) 2 · 6H 2O, HL − and 1,10-phenanthroline or 2,6-bis(pyrazol-1-yl)pyridine (bppy) in MeCN gave complexes [Cu 2(HL) 3(phen) 2](ClO 4) ( 1) and [Cu 2(HL) 2(bppy) 2](ClO 4) 2 ( 3), respectively. The same reaction systems in MeOH afforded the new complexes [Cu 2L′ 2(ClO 4)(phen) 2(MeOH)](ClO 4) ( 2b) and [Cu 2L′ 2(bppy) 2](ClO 4) 2 ( 4) in which the maleamate(−1) ion has been transformed to the monomethyl maleate(−1) ligand L′ − via a novel, metal ion-assisted process. The reaction that leads to 2b takes place through the formation of the 1D coordination polymer [Cu(ClO 4)(phen)(MeOH) 2] n (ClO 4) n ( 2a), whose structure was assigned on the basis of its spectral similarity with the structurally characterized complex [Cu(ClO 4)(phen)(MeCN) 2] n (ClO 4) n ( 2c). Only the carboxylate oxygen atoms of HL − and L′ − are coordinated to copper(II) in 1, 2b, 3 and 4.